Broadband Spectral Reflectance Models of Turfgrass Species and Cultivars to Drought Stress

The objective of this study was to assess canopy broadband spectral reflectance for turfgrasses under drought stress. Optimum turf quality (TQ) and leaf firing (LF) models were developed and compared based on two, three, and five wavelength bands. Sods of bermudagrass (Cynodon dactylon L. x C. transvaalensis Burtt-Davy), seashore paspalum (Paspalum vaginatum Swartz), zoysiagrass (Zoysia japonica Steud.), and St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and seeded tall fescue (Festuca arundinacea Schreb.) were used in this study with three cultivars each of bermudagrass, seashore paspalum, and tall fescue. Traditional vegetation indices (VIs) based on two bands within 660 to 950 nm were not as sensitive as three to five broadband models using a wider band range of 660 to 1480 nm. Optimum models were cultivar specific models, even within a species. The broadband wavelength at R900 and R1200 should be considered in drought sensitive spectral models since they were most often observed and exhibited high partial R2 values. These results suggest that mobile broadband spectral devices to map turfgrass responses to drought stress would benefit by the availability of three to five broadbands that could be user selected for optimum, cultivar specific models.